1. Field of the Invention
This invention relates generally to a fluorescent lamp device, and more particularly to such a device having an incandescent lamp base.
2. Description of the Prior Art
A fluorescent lamp is widely used for its lighting efficiency in comparison with an incandescent lamp. So it is advantageous to use a fluorescent lamp instead of an incandescent lamp from the standpoint of electric power consumption in times of a severe energy crisis.
However, a fluorescent lamp generally has a straight or annular shape and has its own shaped base at its opposite ends. Also it is generally necessary to provide a glow starter and a ballast to light a fluorescent lamp. Consequently, a fluorescent lamp cannot typically be directly coupled to an incandescent lamp base.
Although there have been a few proposed fluorescent lamp devices having an incandescent lamp base, for example shown in U.S. Pat. No. 3,953,761, in such a fluorescent lamp device, the ballast is large and is disposed in the center of the device. As a result, it is difficult if not impossible to dispose a conventional ballast of large size in an incandescent lamp base. However, if a ballast were made small and lightweight it would be possible to dispose such a ballast in an incandescent lamp base.
A small and lightweight ballast is known using a positive characteristic thermistor as disclosed in Japanese Utility Model No. 1018720. However, such a thermistor ballast has a tendency to increase its resistance value as its temperature rises. Thus, as such a ballast is heated to a predetermined temperature, its resistance value rapidly becomes large. However, as the ballast resistance increases the lamp soon stops lighting since it is not possible to supply the lamp filaments with enough current to maintain electric discharge. Therefore, the use of such a thermistor ballast alone, without taking other measures, is not feasible in a fluorescent lamp device.